The present invention relates, in general, to a method and apparatus for dispensing of home care liquid formulations and, more specifically, to a method and apparatus for inducing electric charge onto the home care formulations upon dispensing from the spraying device.
The efficacy of home care liquid formulation sprays depends, in part, upon the distribution of the formulation and how efficiently it contacts the intended target surface. Aerosol sprays may be dispersed into volumes or onto areas as desired. When this is done, however, various air disturbances may prevent droplets from reaching the intended target material or from sufficiently reaching all of the desired surface area.
The probability of droplets reaching their target(s) may be increased, if the droplets are electrically charged. By electrically charging the droplets, the target materials or target areas, which are at a different electrical potential, form an attraction with the droplets. This improves the efficacy of the formulation.
Spraying apparatus for producing a spray of liquid droplets is well known. For example, such apparatus is known in the domestic environment for producing sprays of droplets of liquid home care products. Generally, such apparatus includes a reservoir for accommodating the liquid composition to be sprayed, a spraying head including a bore through which the composition is expelled in the form of a spray of droplets, and a conduit system whereby the composition may pass from the reservoir to the spraying head. The apparatus may be in the form of an aerosol, in which case it includes gas under pressure, which expels the liquid composition from the reservoir to the spraying head and then out of the spraying head in the form of a spray of droplets.
Generally, the droplets leaving the spraying head have a small electrostatic charge created by electron transfer between the liquid and the walls of the apparatus. It is known that it is necessary to increase the level of charge on the droplets significantly to enable electrostatic attraction to insects.
It is also known that components of the apparatus in contact with the liquid have the ability to influence the charge given to the liquid as it is being sprayed. More particularly, it has been found that the charge on the droplets increases with an increase in contact area between the liquid and the bore-defining portions of the spraying head.
One specific home care product application is insecticides. International Publication Number WO099/01227 discloses a method of killing flying insects using electrostatically charged droplets of an insecticidal formulation having a charge-to-mass ratio of approximately xc2x11xc3x9710xe2x88x924 Coulombs/kilogram (C/kg). The charge is imported to the liquid droplets by double layer charging. The charge is dispersed as the liquid is aerosolized.
Various characteristics of an aerosol spray device may increase double layer charging and charge exchange between the liquid formulation and the surfaces of the components of the aerosol spray device. Such increases may be brought about by factors increasing the turbulence of the flow through the device, and increasing the frequency and velocity of contact between the liquid and the internal surfaces of the container, valve and actuator.
A need still exists for a spraying device that dispenses electrostatic liquid droplets by methods that develop charging of a liquid formulation. A need also exists for dispensing the electrostatic liquid droplets from a standard domestic aerosol can using a method that reliably and robustly induces a charge of desired polarity on the formulation as it is sprayed.
To meet this and other needs, and in view of its purposes, the present invention provides a spraying device for dispensing electrostatic liquid droplets. The device includes a container holding a liquid at one end, and having a nozzle assembly with an aperture at another end. The nozzle assembly includes a longitudinal hollow tube terminating in a metallic structure. The structure includes a metallic base plate having at least one aperture formed therein. The longitudinal hollow tube is inserted in the aperture for fluid communication with the liquid. A charge accumulator disposed in the liquid accumulates electrostatic charges. A wire conductor between the base plate and the charge accumulator transfers the electrostatic charges from the liquid to the nozzle assembly.
In one embodiment, the charge accumulator includes first and second opposing surfaces separated by a space, the space containing polymer beads and liquid. The first and second surfaces are each formed from a material selected from one end of the Triboelectric Series and the polymer beads are formed from another material selected from another end of the Triboelectric Series. A metallic wire mesh is included in the second surface. When shaking the container, the polymer beads move against the opposing surfaces and the electrostatic charges are accumulated on the metallic wire mesh.
In another embodiment, the charge accumulator includes a flywheel oriented to intercept a liquid stream flowing into the longitudinal hollow tube. A voltage generator is engagingly coupled by a shaft to the flywheel and provides electrostatic charges when the flywheel rotates by pressure from the liquid stream flowing to the nozzle. A conductor wire between the voltage generator and the nozzle brings the charges to the droplets as they are being sprayed out of the container.
It is understood that the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.